Technical Field
The present invention relates to a coil component having a bobbin base and a coil, and is typically used for a transformer, and a method of manufacturing such coil component.
Related Art
A variety of coil components, having a wire-wound coil, and a core (magnetic core) inserted therein, composed of a magnetic material, have been proposed.
Regarding this type of coil component, JP-U-H05-28012 describes a coil component in which a pair of cores (magnetic components), each having a groove formed on the outer circumference thereof, are abutted and bound by placing a tape so as to surround them while guided by the grooves. According to the description, the pair of magnetic components may be prevented from shifting from each other, and thereby a magnetic path having a desired shape may be formed in a stable manner.
JP-A-2010-165857 describes a coil component in which a first core and a second core, composed of a magnetic material and respectively having magnetic legs, are inserted into a bobbin having a coil wound therearound, so as to abut the magnetic legs, and the bonded portion is pressurized inwardly using an elastic member such as heat shrinkable tube. By using the bobbin, like the coil component described in JP-A-2010-165857, a bobbin and a coil having arbitrary shapes may be formed easily, and the core is prevented from being damaged by winding tension applied in the process of wire winding. According to JP-A-2010-165857, the heat shrinkable tube is wound around the outer side of the magnetic legs and the outer surface of the coil, in the direction normal to the winding axial direction of the bobbin. In this way, the pair of the first and second cores and the coil are joined by the heat shrinkable tube making use of frictional force.
In the coil components described in JP-U-H05-28012 and JP-A-2010-165857, a single magnetic core is configured by combining the pair of magnetic components which are inserted into the coil from both sides thereof in the winding axial direction.
A shift in the relative position of the coil and the magnetic core unfortunately causes fluctuation in inductance which is one of important characteristics of the coil component. In the coil component of JP-U-H05-28012, the pair of magnetic component, each having an “E-shape”, are abutted and fixed by the tape, to configure the magnetic core. However, for the reasons regarding molding, a gap is inevitably produced between a center leg of the magnetic core and a center hole of an air-core coil, and this may cause a shift in the relative position between the magnetic and the air-core coil. Also in the coil component of JP-A-2010-165857, the magnetic core and the bobbin may cause positional shift in the process of assemblage, since the pair of magnetic components (first core, second core) and the coil are simply bound only with the aid of frictional force, while being pressurized by the heat shrinkable tube. As a consequence, the relative position between the magnetic core and the coil may vary, and the inductance may fluctuate. It has therefore been difficult for the coil components as disclosed in JP-U-H05-28012 and JP-A-2010-165857, to fix at least three components, including the pair of magnetic components and the core, without causing a shift in the relative position. This has caused variation in the inductance from product to product, and has degraded stability in product characteristics.
Meanwhile, one possible technique of fixing a desired relative position between the pair of magnetic components and the bobbin may be bonding of these members with an adhesive, while holding them using a special jig. This is however disadvantageous in terms of cost, since there are diversified shapes of the coil components, and this needs provision of special jigs for every product. Also the number of manufacturing processes will increase, due to needs for attaching these members to the jig, and then detaching them from the jig.